<template>
    <div class="pagination">
        <!-- 上 -->
        <button :disabled="pageNo == 1" @click="$emit('getPageNo', pageNo - 1)">
            上一页
        </button>
        <button
                v-if="startNumAndEndNum.start > 1"
                @click="$emit('getPageNo', 1)"
                :class="{ active: pageNo == 1 }"
        >
            1
        </button>
        <button v-if="startNumAndEndNum.start > 2">···</button>
        <!-- 中间部分 -->
        <button
                v-for="(page, index) in startNumAndEndNum.end"
                :key="index"
                v-if="page >= startNumAndEndNum.start"
                @click="$emit('getPageNo', page)"
                :class="{ active: pageNo == page }"
        >
            {{ page }}
        </button>

        <!-- 下 -->
        <button v-if="startNumAndEndNum.end < totalPage - 1">···</button>
        <button
                v-if="startNumAndEndNum.end < totalPage"
                @click="$emit('getPageNo', totalPage)"
                :class="{active:pageNo==totalPage}"
        >
            {{ totalPage }}
        </button>
        <button
                :disabled="pageNo == totalPage"
                @click="$emit('getPageNo', pageNo + 1)"
        >
            下一页
        </button>

        <button style="margin-left: 30px">共 {{ total }} 条</button>
    </div>
</template>

<script>
    export default {
        name: "Pagination",
        props: ["pageNo", "pageSize", "total", "continues"],
        computed: {
            //总共多少页
            totalPage() {
                //向上取证
                return Math.ceil(this.total / this.pageSize);
            },
            //计算出连续的页码的起始数字与结束数字[连续页码的数字:至少是5]
            startNumAndEndNum() {
                const { continues, pageNo, totalPage } = this;
                //先定义两个变量存储起始数字与结束数字
                let start = 0,
                    end = 0;
                //连续页码数字5【就是至少五页】，如果出现不正常的现象【就是不够五页】
                //不正常现象【总页数没有连续页码多】
                if (continues > totalPage) {
                    start = 1;
                    end = totalPage;
                } else {
                    //正常现象【连续页码5，但是你的总页数一定是大于5的】
                    //起始数字
                    start = pageNo - parseInt(continues / 2);
                    //结束数字
                    end = pageNo + parseInt(continues / 2);
                    //把出现不正常的现象【start数字出现0|负数】纠正
                    if (start < 1) {
                        start = 1;
                        end = continues;
                    }
                    //把出现不正常的现象[end数字大于总页码]纠正
                    if (end > totalPage) {
                        end = totalPage;
                        start = totalPage - continues + 1;
                    }
                }
                return { start, end };
            },
        },
    };
</script>

<style lang="less" scoped>
    .pagination {
        text-align: center;
        button {
            margin: 0 5px;
            background-color: #f4f4f5;
            color: #606266;
            outline: none;
            border-radius: 2px;
            padding: 0 4px;
            vertical-align: top;
            display: inline-block;
            font-size: 13px;
            min-width: 35.5px;
            height: 28px;
            line-height: 28px;
            cursor: pointer;
            box-sizing: border-box;
            text-align: center;
            border: 0;

            &[disabled] {
                color: #c0c4cc;
                cursor: not-allowed;
            }

            &.active {
                cursor: not-allowed;
                background-color: #409eff;
                color: #fff;
            }
        }
    }
    .active{
        background: skyblue;
    }
</style>
